Larger quantities of purified photoreactivating enzyme from dried Baker's yeast will be prepared and studied. If homogeneous, its properties will be measured and the chromophore isolated and identified. If it is not homogeneous, fractionation will continue until it is homogeneous. A. The features of DNA recognized by competent cells will be determined. B. Search for the cellular components which interact with DNA and reflect the specificity. C. Develop a vesicle system capable of taking up DNA.